Variable speed accessory drive system

ABSTRACT

The present invention provides an accessory drive system for a vehicle. The accessory drive system includes a planetary gear set having a first, second, and third planetary member. A torque transfer device operatively connects an engine with the first planetary member. A motor/generator is operatively connected to the second planetary member, and a plurality of accessories are operatively connected to the third planetary member. Engine output is transferable through the planetary gear set to drive the accessories, and the speed at which the accessories are driven is selectable by controlling the speed of the motor/generator.

TECHNICAL FIELD

The present invention pertains generally to a variable speed accessorydrive system for a vehicle.

BACKGROUND OF THE INVENTION

Driven accessories in a vehicle may include, for example, an airconditioning compressor, a power steering pump, and an alternator. Theseaccessories are generally powered by output from the engine.Conventional automotive accessory drive systems include a drive pulleyconnected to an engine output shaft. A flexible chain or belt couplesthe drive pulley with a plurality of driven pulleys that are eachoperatively connected to an accessory. The operating speeds of theaccessories in such a conventional drive system are directlyproportional to the speed of the engine. Since the engine operates overa wide speed range (i.e., for example, between 500 rpm and 7,000 rpm),the accessories are typically designed to provide full capacity at thelow end of the engine speed range in order to ensure that they remainoperational. Therefore, at higher engine speeds, excess energytransferred to the accessories may be lost.

SUMMARY OF THE INVENTION

The present invention provides an accessory drive system for a vehicle.The accessory drive system includes a planetary gear set having a first,second, and third planetary member. A first torque transfer deviceoperatively connects an engine with the first planetary member. Amotor/generator is operatively connected to the second planetary member,and a plurality of accessories are operatively connected to the thirdplanetary member through a second torque transfer device. Engine outputis transferable through the planetary gear set to drive the accessories,and the speed at which the accessories are driven is selectable bycontrolling the speed of the motor/generator.

According to the preferred embodiment, the first planetary member is aring gear member, the second planetary member is a sun gear member, andthe third planetary member is a planet carrier member.

According to an alternate embodiment, the first planetary member is asun gear member, the second planetary member is a planet carrier member,and the third planetary member is a ring gear member.

According to another alternate embodiment, the first planetary member isa ring gear member, the second planetary member is a planet carriermember, and the third planetary member is a sun gear member.

According to another alternate embodiment, the first planetary member isa planet carrier member, the second planetary member is a ring gearmember, and the third planetary member is a sun gear member.

According to another alternate embodiment, the first planetary member isa planet carrier member, the second planetary member is a sun gearmember, and the third planetary member is a ring gear member.

According to another alternate embodiment, the first planetary member isa sun gear member, the second planetary member is a ring gear member,and the third planetary member is a planet carrier member.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of an accessory drive system for avehicle;

FIG. 2 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with the preferred embodiment of thepresent invention;

FIG. 3 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 4 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 5 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 6 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 7 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 8 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 9 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention;

FIG. 10 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention; and

FIG. 11 is a more detailed schematic depiction of the accessory drivesystem of FIG. 1 in accordance with an alternate embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Conventional accessory drive systems operate by transferring engineoutput directly to the accessories so the accessories are driven at aspeed directly proportional to engine speed. Since the engine operatesover a wide speed range (e.g., between 500 rpm and 7,000 rpm), theaccessories are typically designed to provide full capacity at the lowend of the engine speed range in order to ensure they remain fullyoperational. Therefore, when the engine is operating at higher speeds,conventional accessory drive systems transfer more energy to theaccessories than necessary to provide adequate function. The excessenergy transferred to the accessories causes inefficiency and diminishesfuel economy. The accessory drive system 10 (shown in FIG. 1) of thepresent invention allows the accessories to be driven at a predeterminedoptimal speed independent from the speed at which the engine is runningin order to improve fuel economy. The predetermined optimal speed atwhich the accessories are driven may, for example, be a continuouslycalculated variable speed selected to optimally meet the needs andconditions of a particular application.

Referring to FIG. 1, a schematic representation of an accessory drivesystem 10 for a vehicle is shown. The accessory drive system 10 includesan engine 12 configured to transmit output to a crank pulley 14 via acrankshaft or output shaft 16. Alternatively, engine output may betransferred to the crank pulley 14 in any known manner such as, forexample, via a power take-off (not shown). A first belt or chain 18couples the crank pulley 14 with an accessory drive input pulley 20. Theaccessory drive input pulley 20 is operatively connected to adifferential transmission such as the planetary gearset 22. It should beappreciated that the accessory drive input pulley 20 may be directlyconnected to the planetary gearset 22, or may be indirectly connected tothe planetary gearset 22 such as, for example, through a gear assembly(not shown). The planetary gearset 22 has a plurality of membersincluding: a sun gear 24; a plurality of pinions or planet gears 26; aring gear 28; and a pinion carrier or planet carrier 30.

The engine 12 also transfers output via the crankshaft 16 to atransmission 17. The transmission 17 transfers output from the engine 12to a plurality of wheels 19 in order to drive a vehicle. It should beappreciated that the transmission 17 and wheels 19 may include any knownconfigurations and are not included as part of the accessory drivesystem 10 of the present invention.

The planetary gearset 22 is configured to convert the rotationalvelocity of the accessory drive input pulley 20 (which runs at a fixedratio of engine speed) to a predetermined value selected to efficientlydrive the accessories 38. In other words, the planetary gearset 22 canselectively increase or decrease the magnitude of the rotationalvelocity from the accessory drive input pulley 20 in order to drive theaccessories 38 at more efficient speed and thereby improve fuel economy.Output from the planetary gearset 22 is transferred to an accessorydrive output pulley 32. A second belt or chain 34 couples the accessorydrive output pulley 32 with one or more accessory pulleys 36. Theaccessory pulleys 36 are each operatively connected to an accessory 38.

A motor/generator 40 is configured to selectively transfer torque to theplanetary gearset 22 either directly or through a transfer device suchas, for example, a belt, chain, gear assembly, differential gear, etc.The motor/generator 40 is configured to receive power from and/ortransfer power to a storage device such as the battery 46. As is knownin the art, by transferring a first predetermined amount of input torquefrom the engine 12 to one of the planetary gear set 22 members, andtransferring a second predetermined amount of input torque from themotor/generator 40 to another of the planetary gear set 22 members, theplanetary gear set 22 can be controlled to produce a selectable amountof output torque from yet another of its members. Therefore, bycontrolling the amount of torque transferred from the motor generator 40to the planetary gear set 22, the planetary gear set 22 output speed isselectable within an operational range.

The engine 12 and the motor/generator 40 are operatively connected to acontroller 42. The controller 42 may also be operatively connected toone or more sensors (not shown) implemented to select an optimal outputspeed for the planetary gear set 22. The controller 42 receives inputfrom the engine 12 indicating the current engine speed and calculates acorresponding motor/generator 40 speed or torque value required toproduce the predetermined optimal planetary gear set 22 output speed. Asan example, if the engine 12 is running at 4,000 rpm and the accessories38 are optimized to run at 1,500 rpm, the controller 42 calculates themotor/generator 40 speed required to produce a planetary gear set 22output speed of 1,500 rpm. These types of calculations which utilize thering/sun tooth ratios of a planetary gear set are well known to thoseskilled in the art and therefore will not be described in detailhereinafter. After calculating, the controller 42 commands themotor/generator 40 to transfer the required amount of torque to theplanetary gear set 22 such that the accessories 38 are driven in anoptimally efficient manner.

The accessory drive system 10 of the present invention may, in somecases, be implemented to drive the accessories (not shown) of a vehiclewhen the engine is off. If, for example, the vehicle's engine (notshown) provides sufficient rotational resistance when off to effectivelyrestrain the planetary member (not shown) connected thereto, amotor/generator (not shown) can be implemented to drive the accessories.The engine's rotational resistance is proportional to the force requiredto cyclically translate the engine components such as the engine pistons(not shown) when the engine is off. Therefore, if the amount of torquerequired to drive all the accessories causes a reaction torque at theengine which is less than the engine rotational resistance, theaccessories can be driven by the motor/generator without also drivingthe engine.

Having explained the components and functionality of the accessory drivesystem 10, the precise interconnection of these components will now bedescribed in accordance with a plurality of different embodiments. FIGS.2-11 each illustrate a separate embodiment that functions similarly tothe previously described accessory drive system 10, but includessomewhat different component connections. Like reference numbers areused in FIGS. 2-11 to refer to like components from FIG. 1.Additionally, the letters “a” through “j” added as a suffix to areference numeral identifies a similar component in a differentembodiment. As an example, the engine 12 of FIG. 1 functions similarlyto the engines 12 a-12 j of FIGS. 2-11, respectively. Therefore, unlessspecified otherwise, the components of FIGS. 2-11 identified with a basereference number followed by one of the letters “a” through “j” shouldbe considered to be identical to a respective component of FIG. 1identified with a common base reference number.

Referring to FIG. 2, an accessory drive system 10 a is shown inaccordance with the preferred embodiment of the present invention. Theaccessory drive input pulley 20 a (which runs at a fixed ratio of enginespeed) is operatively connected to the ring gear 28 a of the planetarygear set 22 a. The motor/generator 40 a is operatively connected to thesun gear 24 a of the planetary gear set 22 a. The planet carrier 30 a ofthe planetary gear set 22 a is operatively connected to the accessorydrive output pulley 32 a. Therefore, in response to input from theengine 12 a (via the ring gear 28 a) and/or the motor/generator 40 a(via the sun gear 24 a), the planetary gear set 22 a can transfer outputto the accessory drive output pulley 32 a (via the planet carrier 30 a)and thereby drive the accessories 38 a at a selectable rate.

Referring to FIG. 3, an accessory drive system 10 b is shown inaccordance with an alternate embodiment of the present invention. Theplanetary gear set 22 b of this embodiment preferably includes adouble-pinion carrier 30 b configuration. The accessory drive inputpulley 20 b (which runs at a fixed ratio of engine speed) is operativelyconnected to the sun gear 24 b of the planetary gear set 22 b. Themotor/generator 40 b is operatively connected to the double-pinioncarrier 30 b of the planetary gear set 22 b. The ring gear 28 b of theplanetary gear set 22 b is operatively connected to the accessory driveoutput pulley 32 b. Therefore, in response to input from the engine 12 b(via the sun gear 24 b) and/or the motor/generator 40 b (via thedouble-pinion carrier 30 b), the planetary gear set 22 b can transferoutput to the accessory drive output pulley 32 b (via the ring gear 28b) and thereby drive the accessories 38 b at a selectable rate.

Referring to FIG. 4, an accessory drive system 10 c is shown inaccordance with an alternate embodiment of the present invention. Theplanetary gear set 22 c of this embodiment preferably includes adouble-pinion carrier 30 c configuration. The accessory drive inputpulley 20 c (which runs at a fixed ratio of engine speed) is operativelyconnected to the ring gear 28 c of the planetary gear set 22 c. Themotor/generator 40 c is operatively connected to the double-pinioncarrier 30 c of the planetary gear set 22 c. The sun gear 24 c of theplanetary gear set 22 c is operatively connected to the accessory driveoutput pulley 32 c. Therefore, in response to input from the engine 12 c(via the ring gear 28 c) and/or the motor/generator 40 c (via thedouble-pinion carrier 30 c), the planetary gear set 22 c can transferoutput to the accessory drive output pulley 32 c (via the sun gear 24 c)and thereby drive the accessories 38 c at a selectable rate.

Referring to FIG. 5, an accessory drive system 10 d is shown inaccordance with an alternate embodiment of the present invention. Theaccessory drive input pulley 20 d (which runs at a fixed ratio of enginespeed) is operatively connected to the planet carrier 30 d of theplanetary gear set 22 d. The motor/generator 40 d is operativelyconnected to the ring gear 28 d of the planetary gear set 22 d. The sungear 24 d of the planetary gear set 22 d is operatively connected to theaccessory drive output pulley 32 d. Therefore, in response to input fromthe engine 12 d (via the planet carrier 30 d) and/or the motor/generator40 d (via the ring gear 28 d), the planetary gear set 22 d can transferoutput to the accessory drive output pulley 32 d (via the sun gear 24 d)and thereby drive the accessories 38 d at a selectable rate.

Referring to FIG. 6, an accessory drive system 10 e is shown inaccordance with an alternate embodiment of the present invention. Theaccessory drive input pulley 20 e (which runs at a fixed ratio of enginespeed) is operatively connected to the planet carrier 30 e of theplanetary gear set 22 e. The motor/generator 40 e is operativelyconnected to the sun gear 24 e of the planetary gear set 22 e. The ringgear 28 e of the planetary gear set 22 e is operatively connected to theaccessory drive output pulley 32 e. Therefore, in response to input fromthe engine 12 e (via the planet carrier 30 e) and/or the motor/generator40 e (via the sun gear 24 e), the planetary gear set 22 e can transferoutput to the accessory drive output pulley 32 e (via the ring gear 28e) and thereby drive the accessories 38 e at a selectable rate.

Referring to FIG. 7, an accessory drive system 10 f is shown inaccordance with an alternate embodiment of the present invention. Theaccessory drive input pulley 20 f (which runs at a fixed ratio of enginespeed) is operatively connected to the sun gear 24 f of the planetarygear set 22 f. The motor/generator 40 f is operatively connected to thering gear 28 f of the planetary gear set 22 f. The planet carrier 30 fof the planetary gear set 22 f is operatively connected to the accessorydrive output pulley 32 f. Therefore, in response to input from theengine 12 f (via the sun gear 24 f) and/or the motor/generator 40 f (viathe ring gear 24 f), the planetary gear set 22 f can transfer output tothe accessory drive output pulley 32 f (via the planet carrier 30 f) andthereby drive the accessories 38 f at a selectable rate.

Referring to FIG. 8, an accessory drive system 10 g is shown inaccordance with an alternate embodiment of the present invention. Inaddition to the previously identified accessory drive system componentsof the preferred embodiment, the accessory drive system 10 g alsoincludes a second planetary gear set 52 g operatively connected to theplanetary gear set 22 g. The second planetary gear set 52 g includes asun gear 54 g, a plurality of planet gears 56 g, a ring gear 58 g, and aplanet carrier 60 g.

The accessory drive input pulley 20 g (which runs at a fixed ratio ofengine speed) is operatively connected to the ring gear 28 g of theplanetary gear set 22 g. The ring gear 58 g of the second planetary gearset 52 g is operatively connected to the sun gear 24 g of the planetarygear set 22 g. The motor/generator 40 g is operatively connected to thesun gear 54 g of the second planetary gear set 52 g. The planet carrier30 g of the planetary gear set 22 g is operatively connected to theaccessory drive output pulley 32 g, and the planet carrier 60 g of thesecond planetary gear set 52 g is grounded or held stationary at ground48 g. Therefore, in response to input from the engine 12 g (via the ringgear 28 g) and/or the motor/generator 40 g (via the sun gear 54 g), theplanetary gear sets 22 g, 52 g can transfer output to the accessorydrive output pulley 32 g (via the planet carrier 30 g) and thereby drivethe accessories 38 g at a selectable rate.

Referring to FIG. 9, an accessory drive system 10 h is shown inaccordance with an alternate embodiment of the present invention. Inaddition to the previously identified accessory drive system componentsof the preferred embodiment, the accessory drive system 10 h alsoincludes a second planetary gear set 52 h operatively connected to theplanetary gear set 22 h. The second planetary gear set 52 h includes asun gear 54 h, a plurality of planet gears 56 h, a ring gear 58 h, and aplanet carrier 60 h.

The accessory drive input pulley 20 h (which runs at a fixed ratio ofengine speed) is operatively connected to the sun gear 24 h of theplanetary gear set 22 h. The planet carrier 60 h of the second planetarygear set 52 h is operatively connected to the ring gear 28 h of theplanetary gear set 22 h. The motor/generator 40 h is operativelyconnected to the ring gear 58 h of the second planetary gear set 52 h.The ring gear 28 h of the planetary gear set 22 h is operativelyconnected to the accessory drive output pulley 32 h. Therefore, inresponse to input from the engine 12 h (via the sun gear 24 h) and/orthe motor/generator 40 h (via the ring gear 58 h), the planetary gearsets 22 h, 52 h can transfer output to the accessory drive output pulley32 h (via the ring gear 28 h) and thereby drive the accessories 38 h ata selectable rate.

Referring to FIG. 10, an accessory drive system 10 i is shown inaccordance with an alternate embodiment of the present invention. Theplanetary gear set 22 i of this embodiment preferably includes adouble-pinion carrier 30 i configuration. The accessory drive inputpulley 20 i (which runs at a fixed ratio of engine speed) is operativelyconnected to the ring gear 28 i of the planetary gear set 22 i. A gearassembly 64 i couples the motor/generator 40 i with the double-pinioncarrier 30 i of the planetary gear set 22 i. The sun gear 24 i of theplanetary gear set 22 i is operatively connected to the accessory driveoutput pulley 32 i. Therefore, in response to input from the engine 12 i(via the ring gear 28 i) and/or the motor/generator 40 i (via thedouble-pinion carrier 30 i), the planetary gear set 22 i can transferoutput to the accessory drive output pulley 32 i (via the sun gear 24 i)and thereby drive the accessories 38 i at a selectable rate.

Referring to FIG. 11, an accessory drive system 10 j is shown inaccordance with an alternate embodiment of the present invention. Theaccessory drive input pulley 20 j (which runs at a fixed ratio of enginespeed) is operatively connected to the planet carrier 30 j of theplanetary gear set 22 j. A third belt or chain 66 j couples themotor/generator 40 j and the sun gear 24 j of the planetary gear set 22j. The ring gear 28 j of the planetary gear set 22 j is operativelyconnected to the accessory drive output pulley 32 j. Therefore, inresponse to input from the engine 12 j (via the planet carrier 30 j)and/or the motor/generator 40 j (via the sun gear 24 j), the planetarygear set 22 j can transfer output to the accessory drive output pulley32 j (via the ring gear 28 j) and thereby drive the accessories 38 j ata selectable rate.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. An accessory drive system for a vehicle comprising: an engine; anaccessory operatively connected to the engine; a planetary gear setdisposed between the engine and the accessory; a motor/generatoroperatively connected to the planetary gear set; wherein output fromsaid engine is transferable through the planetary gear set to drive theaccessories, and the speed at which the accessories are driven isselectable by controlling the speed of the motor/generator.
 2. Theaccessory drive system of claim 1, further comprising a plurality ofpulleys configured to transfer output from the engine to theaccessories.
 3. The accessory drive system of claim 1, furthercomprising at least one belt operatively connecting said plurality ofpulleys.
 4. The accessory drive system of claim 1, further comprising agear assembly operatively connecting the motor/generator to theplanetary gear set.
 5. The accessory drive system of claim 1, furthercomprising a second planetary gear set operatively connected between theengine and the accessory.
 6. An accessory drive system for a vehiclecomprising: a planetary gear set having a first, second, and thirdplanetary member; an engine operatively connected to the first planetarymember; a motor/generator operatively connected to the second planetarymember; and a plurality of accessories operatively connected to thethird planetary member; wherein engine output is transferable throughthe planetary gear set to drive the plurality of accessories, and thespeed at which the plurality of accessories are driven is selectable bycontrolling the torque transfer from the motor/generator to the secondplanetary member.
 7. The accessory drive system of claim 6, wherein thefirst planetary member is a ring gear member, the second planetarymember is a sun gear member, and the third planetary member is a planetcarrier member.
 8. The accessory drive system of claim 6, wherein thefirst planetary member is a sun gear member, the second planetary memberis a planet carrier member, and the third planetary member is a ringgear member.
 9. The accessory drive system of claim 6, wherein the firstplanetary member is a ring gear member, the second planetary member is aplanet carrier member, and the third planetary member is a sun gearmember.
 10. The accessory drive system of claim 6, wherein the firstplanetary member is a planet carrier member, the second planetary memberis a ring gear member, and the third planetary member is a sun gearmember.
 11. The accessory drive system of claim 6, wherein the firstplanetary member is a planet carrier member, the second planetary memberis a sun gear member, and the third planetary member is a ring gearmember.
 12. The accessory drive system of claim 6, wherein the firstplanetary member is a sun gear member, the second planetary member is aring gear member, and the third planetary member is a planet carriermember.
 13. The accessory drive system of claim 6, further comprising agear assembly operatively connecting the motor/generator to the secondplanetary member.
 14. The accessory drive system of claim 6, furthercomprising a belt operatively connecting the motor/generator to thesecond planetary member.
 15. The accessory drive system of claim 6,further comprising a chain operatively connecting the motor/generator tothe second planetary member.
 16. The accessory drive system of claim 6,wherein one of the first, second, and third planetary members is adouble-pinion carrier.
 17. The accessory drive system of claim 6,wherein one of the first, second, and third planetary members is asingle-pinion carrier.
 18. An accessory drive system comprising: aplanetary gear set having a first, second, and third planetary member; afirst torque transfer apparatus operatively connecting an engine to thefirst planetary member; a second torque transfer apparatus operativelyconnecting a motor/generator to the second planetary member; and anaccessory operatively connected to the third planetary member; whereinthe engine provides sufficient rotational resistance while off torestrain the first planetary member from rotating and thereby allow themotor/generator to drive the accessory without also driving the engine.19. The accessory drive system of claim 18, wherein the first and secondtorque transfer apparatus includes a gear assembly.
 20. The accessorydrive system of claim 18, further comprising a chain operativelyconnecting the motor/generator to the second planetary member.